1. Field of the Invention
This invention relates to magnetic disk information storage apparatus utilizing a removable head/disk assembly.
The term "head/disk assembly" or "HDA" is often employed to denote a subassembly which is neither customer removable nor a separate product but which may be removed and reinstalled by a maintenance engineer. As used here, "head/disk assembly" is intended to apply generically not only to such subassemblies, but also to customer removable and interchangeable "data modules," marketed as separate products, and which include both heads and disks.
2. Description of the Prior Art
The advantages of a modular construction of disk file in which disks and movable heads are enclosed in a sealable module or subassembly are discussed in U.S. Pat. Nos. 3,786,454, Ser. No. 206,688, filed Dec. 10, 1971 in behalf of R. W. Lissner and R. B. Mulvany and 3,849,800, Ser. No. 231,320, filed Mar. 2, 1972 in behalf of D. E. Cuzner et al, both assigned to the assignee of the present invention. Modular construction provides either interchangeability of stored data between files for a customer as in U.S. Pat. No. 3,786,454 or else, as in U.S. Pat. No. 3,849,800 it provides ease of assembly and disassembly for manufacture or servicing. Permanently associating heads and disks in the same assembly reduces tolerance requirements. Furthermore, the assemblies are easily sealed and the heads and disks can be maintained in a very clean environment to reduce the risk of contaminants interfering with the flying properties of the heads at spacings as low as 50 microinches. Finally, employment of a head/disk assembly allows the possibility of isolating the heads and disks to some extent from vibrations generated elsewhere within the apparatus.
U.S. Pat. No. 3,849,800 specifically discloses a magnetic disk apparatus including a sealed module which encloses a magnetic disk, magnetic heads incorporated in head/arm assemblies, an electromagnetic actuator for positioning the magnetic heads on the head/arm assemblies relative to the disk and a drive spindle on which the disk is seated. The weight of the module includes the weight of the actuator magnet structure which is mounted on the same base casting as the drive spindle and disks. The spindle and disks are thus directly subject to vibrations induced by reaction of the actuator magnet structure during operation of the actuator. For a multi disk file, particularly of the type in which a great number of head/arm assemblies are mounted for linear motion on the carriage, a very much larger and stronger magnet structure would have to be employed. Any attempt to decrease access time would also require a stronger and therefore, generally, heavier magnet structure. This would lead to disadvantages both in terms of increased weight and increased reaction forces.
U.S. Pat. No. 3,786,454 discloses a disk storage apparatus including an interchangeable sealed cartridge, enclosing magnetic disks, accessing magnetic head/arm assemblies, a movable carriage to which the head arms are mounted, and a drive spindle on which the disks are seated. For accessing the heads to selected data tracks, coupling means are provided to engage the carriage and head arm assemblies with a voice coil motor, disposed in a disk file housing for accommodating the cartridge. The file housing includes a drive motor coupled by pulley means, for example, to the enclosed spindle to provide rotary motion to the disks.
The coupling means is a relatively complex mechanism. Attached to the coil of the voice coil motor is a spring loaded coupling pin and operating shaft. A support and actuator mechanism is also provided in the file housing for supporting the coil when not coupled to the carriage and for actuating the operating shaft to effect coupling.
Although it was well known in earlier disk files both of the fixed and removable disk type to employ a linear voice coil actuator in which the actuator coil was permanently coupled to the carriage, such files did not have the many advantages of a modular head/disk assembly enumerated above. One such typical system is shown in U.S. Pat. No. 3,470,399, Ser. No. 737,438, filed June 17, 1968 in behalf of J. J. Johnson and H. C. Stephens and assigned to the same assignee as the present invention.